Heretofore, various proposals have been made with respect to a pneumatic tire for improving a handling performance on snow or ice covered roads by increasing a gripping force (i.e. an edge effect). For example, in a Patent Document listed below, disclosed is a pneumatic tire in which lateral sipes extending along a tread width direction are provided on blocks segmented by circumferential grooves and lateral grooves.
In this pneumatic tire, the edge effect can be exerted sufficiently at starting and braking, and thereby a handling performance (especially, a startup accelerating performance and a braking performance) is made improved. However, according to this pneumatic tire, friction between its tread and a road surface becomes small while cornering, and thereby sideslips may occur. In recent pneumatic tires, circumferential sipes extending along a tire circumferential direction are provided on its blocks to restrain such sideslips. In a Patent Document 2 listed below, disclosed is a pneumatic tire in which circumferential sipes extending along a tire circumferential direction and extending straight along a tire radial direction are provided in its blocks.
Patent Document 1: Japanese Patent Application Laid-Open NO. 2000-190711 (pages 2 to 4, FIG. 1)
Patent Document 2: Japanese Patent Application Laid-Open NO. 2002-254906 (pages 2 and 3, FIG. 1)